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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

The 97% consensus on global warming

What the science says...

Climate Myth...

There is no consensusThe Petition Project features over 31,000 scientists signing the petition stating "There is no convincing scientific evidence that human release of carbon dioxide will, in the forseeable future, cause catastrophic heating of the Earth's atmosphere ...". (Petition Project)

Science achieves a consensus when scientists stop arguing. When a question is first asked – like ‘what would happen if we put a load more CO2 in the atmosphere?’ – there may be many hypotheses about cause and effect. Over a period of time, each idea is tested and retested – the processes of the scientific method – because all scientists know that reputation and kudos go to those who find the right answer (and everyone else becomes an irrelevant footnote in the history of science). Nearly all hypotheses will fall by the wayside during this testing period, because only one is going to answer the question properly, without leaving all kinds of odd dangling bits that don’t quite add up. Bad theories are usually rather untidy.

But the testing period must come to an end. Gradually, the focus of investigation narrows down to those avenues that continue to make sense, that still add up, and quite often a good theory will reveal additional answers, or make powerful predictions, that add substance to the theory.

So a consensus in science is different from a political one. There is no vote. Scientists just give up arguing because the sheer weight of consistent evidence is too compelling, the tide too strong to swim against any longer. Scientists change their minds on the basis of the evidence, and a consensus emerges over time. Not only do scientists stop arguing, they also start relying on each other's work. All science depends on that which precedes it, and when one scientist builds on the work of another, he acknowledges the work of others through citations. The work that forms the foundation of climate change science is cited with great frequency by many other scientists, demonstrating that the theory is widely accepted - and relied upon.

In the scientific field of climate studies – which is informed by many different disciplines – the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them.

1) Depending on exactly how you measure the expert consensus, it’s somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists.

2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.

Expert consensus results on the question of human-caused global warming among the previous studies published by the co-authors of Cook et al. (2016). Illustration: John Cook. Available on the SkS Graphics page

Scientific consensus on human-caused global warming as compared to the expertise of the surveyed sample. There’s a strong correlation between consensus and climate science expertise. Illustration: John Cook. Available on the SkS Graphics page

Expert consensus is a powerful thing. People know we don’t have the time or capacity to learn about everything, and so we frequently defer to the conclusions of experts. It’s why we visit doctors when we’re ill. The same is true of climate change: most people defer to the expert consensus of climate scientists. Crucially, as we note in our paper:

Public perception of the scientific consensus has been found to be a gateway belief, affecting other climate beliefs and attitudes including policy support.

That’s why those who oppose taking action to curb climate change have engaged in a misinformation campaign to deny the existence of the expert consensus. They’ve been largely successful, as the public badly underestimate the expert consensus, in what we call the “consensus gap.” Only 16% of Americans realize that the consensus is above 90%.

Update

Comments

Concensus only has meaning if there is no pressure to conform in either direction. In the climate debate this is extremely far from being true. How far could we reasonably expect a questioner to go in an IPCC panel when that instantly collects a denialist label and probably guarantees a dead end to even the most able career? In the current climate it is reasonable to assume the dissent camp is at least ten times the admitted size. I know that as an admittedly uninformed questioner I get some pretty vitriolic responses from the eco faithful.

Roverdc hits the nail on the head. To say there is bias in the science at this point is a wild understatement. What the public hears is claims that "all scientists except a few kooks agree that catastrophic global warming is immenent and caused by your car.". This is what they think you mean by consensus.

Is it safe to say the real consensus is closer to the view of those so called deniers in the National Post series or to the alarmist panic that is being widely circulated through things like "An Inconvenient Truth"?

The fact that there are so many Academies of Science endorsing the global warming position is probably the strongest argument for supporting it. The question to ask is how mature is this field? If the answer is 'very mature' then this type of support has high credibility. If the answer is 'immature' then it's significance is considerably less.

Here is a link to US Senate Committee on the Environment that lists in detail 400 scientists who disagree with the anthropomorphic global warming hypothesis:

That there are so many when we repeatedly hear on the news and radio that the actual number of dissenters is 'miniscule' will have the tendency to turn believers into sceptics.

I would also feel more confident if the 'hockey stick' graphics that predict rapid change and global catastrophe would not all be linked back to a small handful of researchers and students who work together and presumably have the same preconceptions and modus operandi. If there are no 'hockey sticks' then the small increase in global temperature over the last century does not statistically look different from what one would expect from natural variation.

The Marshall Institute co-sponsored with the OISM a deceptive campaign -- known as the Petition Project -- to undermine and discredit the scientific authority of the IPCC and to oppose the Kyoto Protocol. Early in the spring of 1998, thousands of scientists around the country received a mass mailing urging them to sign a petition calling on the government to reject the Kyoto Protocol. The petition was accompanied by other pieces including an article formatted to mimic the journal of the National Academy of Sciences. Subsequent research revealed that the article had not been peer-reviewed, nor published, nor even accepted for publication in that journal and the Academy released a strong statement disclaiming any connection to this effort and reaffirming the reality of climate change. The Petition resurfaced in 2001.

They openly lied about endorsement from National Academy of Sciences, were caught, the Academy issues a statement disclaiming any connection, they re-release it again anyways, and you're foolish and gullible enough to buy it and defend it.

Would you like me to post a sample of the signers? That would be embarrassing for you.

i will anyways.........................
The term "scientists" is often used in describing signatories. The petition requests signatories list their degree (B.S., M.S., or Ph.D.) and to list their scientific field.[3] The distribution of petitions was relatively uncontrolled: those receiving the petition could check a line that said "send more petition cards for me to distribute".

The Petition Project itself used to state:
“ Of the 19,700 signatures that the project has received in total so far, 17,800 have been independently verified and the other 1,900 have not yet been independently verified. Of those signers holding the degree of PhD, 95% have now been independently verified. One name that was sent in by enviro pranksters, Geri Halliwell, PhD, has been eliminated. Several names, such as Perry Mason and Robert Byrd are still on the list even though enviro press reports have ridiculed their identity with the names of famous personalities. They are actual signers. Perry Mason, for example, is a PhD Chemist.[2] ”

Asked about the pop singer, Robinson said he was duped. The returned petition, one of thousands of mailings he sent out, identified her as having a degree in microbiology and living in Boston. "It's fake," he said.[15]
”

In 2005, Scientific American reported:
“ Scientific American took a sample of 30 of the 1,400 signatories claiming to hold a Ph.D. in a climate-related science. Of the 26 we were able to identify in various databases, 11 said they still agreed with the petition —- one was an active climate researcher, two others had relevant expertise, and eight signed based on an informal evaluation. Six said they would not sign the petition today, three did not remember any such petition, one had died, and five did not answer repeated messages. Crudely extrapolating, the petition supporters include a core of about 200 climate researchers – a respectable number, though rather a small fraction of the climatological community.[16] ”

In a 2005 op-ed in the Hawaii Reporter, Todd Shelly wrote:
“ In less than 10 minutes of casual scanning, I found duplicate names (Did two Joe R. Eaglemans and two David Tompkins sign the petition, or were some individuals counted twice?), single names without even an initial (Biolchini), corporate names (Graybeal & Sayre, Inc. How does a business sign a petition?), and an apparently phony single name (Redwine, Ph.D.). These examples underscore a major weakness of the list: there is no way to check the authenticity of the names. Names are given, but no identifying information (e.g., institutional affiliation) is provided. Why the lack of transparency?[17]

I have the article you claim was "formatted to mimic..." sitting right here. It doesn't look like it is anything of the sort. In fact it clearly lists Author and who puplished it. It looks like a review of literature type paper which...it is.

As for mass mailing as it was done with a tiny budget it was nothing of the sort. In fact I never even got one despite being on one of the main mailing lists they supposedly used. How many copies of this supposed mass mailing did you get?

Aren't you bothered by a clear attempt by the "enviros" to commit fraud with fake names? Shouldn't you question why they think this is needed or something to be proud of. Is it ok to be dishonest as long as they are on your side?

A sample of 30 in which some back down (people get fired for being skeptics in this field you know)is instantly credible to you while you arm wave away 17,000

You are pointing out 1 fake signature out of 19,000! Really? It was caught, we had thousands of Fake names on our voting list in one nearby city alone.

You are avoiding the main issue. Consensus is not science but if it was the supposed 2500 scientists of the IPCC report have every failing you mention of the petition project and more important the people who signed the petition agreed with what it said. The same can not be said for the IPCC and its supposed 2500. Counted in that IPCC number are hundreds of non scientists, NGO reps (these are people with an agenda)and most importantly reviewers, many of whom don't even agree with the conclusions of the IPCC report. In fact most of the famous "deniers" are included in the 2500 IPCC counts.

Someone made the mistake of asking them after the second IPCC report (surveyed participants) and found that over 60% did not agree with the summary for policy makers.

Maybe we should stop pretending numbers and NGOs are scientists and that consensus is science. It's that claim that raises huge red flags for me.

Let's take a look at the "Inhofe 400"
Meteorologist George Waldenberg was named.
In response to his inclusion ,Mr. Waldenberg sent an email to Senator Inhofes' staff that began
"Marc, Matthew:

Take me off your list of 400 (Prominent) Scientists that dispute Man-Made Global warming claims. I've never made any claims that debunk the "Consensus".

You quoted a newspaper article that's main focus was scoring the accuracy of local weathermen. Hardly Scientific ... yet I'm guessing some of your other sources pale in comparison in terms of credibility.

You also didn't ask for my permission to use these statements. That's not a very respectable way of doing "research".

Again? now its one out of 400 and who the heck was talking about the Inhofe 400?

The point remains it is not a popularity contest despite all the attempted score keeping by the IPCC fans. Also many of the prominent scientists counted in that score are in fact the so called deniers.

the point remains that the deniers flesh out their "petitions" and "lists" with fakes, fraudulent claims, and people who in no way have made any claims against the consensus and pointedly say so.
I've pointed out one of many, (which I've linked to above)
And the "400" was brought up on post#3, which is why I even referred to fraudulent "Petition Project" in the first place.

Well that awful Inhofe 400 is now over 420 as in the time it took for you to complain about the one that didn't sign 20 more "scientists" did. But, it isn't important.

My problem with this is, it isn't an election, you claim the skeptics inflate their numbers, maybe so, beyond question the AGW catastrophy folks inflate theirs. At least two of the best known "deniers" are IPCC lead authors. Dozens of others are listed as contributers or reviewers, several have been so disgusted with the process they withdrew and asked their names be removed. This means they are counted on both sides.

What is that overwelming consensus? Here is what is presented as that consensus: Human CO2 emissions will cause massive catastrophic warming, It will cause disaster in the near future ruining the world for our children. This warming will lead to massive flooding, drought, wide scale starvation, wars, plagues, melting of the polar ice, flooding of huge areas of the world...

Refer to my post number 2 above. Which is closer to the consensus? Al Gore with 23 feet of sea level rise this century or the "deniers" with 15-20 cm ?
Al Gore with his talk of "unprecidented warming". Or the "deniers" claims that the world seems to have wamed about .6-.7 C over the last century and that may be somewhat due to human activity.

Most of the "deniers" probably don't even have that much trouble with the consensus as stated in the first paragraph of the original post. They are vilified largely because they refuse to accept the supposed consensus I just described.

In general I agreed with the stated consensus in the original post, though based on the recent data and the trouble with the historical record I think now I would not use the word "most".

420?
In the original 400 I found many who were completely unqualified, some of whom are skeptical, some of whom are not. Many who are qualified who are either not actually skeptical, are skeptical only of some proposed solutions or who have actually stated their agreement WITH the consensus. The list was not made to hold up to close scrutiny.
I imagine it's the same with the additional 20.

Hey, remember John McLean? The guy who kept steering Andrew Bolt into brick walls? Well he's teamed up with Tom Harris of the NRSP to accuse the IPCC of lying about the scientific support for its reports:

In total, only 62 scientists reviewed the chapter in which this statement appears, the critical chapter 9, "Understanding and Attributing Climate Change". Of the comments received from the 62 reviewers of this critical chapter, almost 60% of them were rejected by IPCC editors. And of the 62 expert reviewers of this chapter, 55 had serious vested interest, leaving only seven expert reviewers who appear impartial.

First, there were much more than 62 reviewers for chapter 9. McLean and Harris have only counted the reviewers of the second order draft and ignored the more numerous comments on the first order draft.

Second, they mislead by giving the impression that 60% of the reviewers disagreed with the IPCC, but half of the comments (572 of them!) were made by Vincent Gray, with 97% of them rejected. Only 16% of the comments by other reviewers were rejected. Gray was also responsible for most the rejected comments on the first order draft. Examples of Gray's rejected comments include:

Insert after "to" "the utterly ridiculous assumption of"

Insert after "Bayesian" "(or super-guesswork)"

Insret before "Calibrated" "Bogus"

Dave Semeniuk has a more detailed analysis of Gray's comments -- 50 of them were Gray repeatedly asking for "anthropogenic" to be replaced with "human-induced".

Third, as Richard Littlemore points out, it is pretty dodgy for the NRSP to complain about "vested interest" when their own vested interest is so blatant. But how did McLean and Harris come up with their claim that 55 of the reviewers had "serious vested interest"? McLean gives details in a piece published by the SPPI (an oil industry funded think tank that apparently does not count as a vested interested to McLean). Scientists were declared to have a vested interest if they were an IPCC author, or an IPCC author of a previous assessment, or if any of their work was cited by the report, or if they worked for a government, or if they work for an organization that gets government funding, or if they have a "possible commercial vested interest in the claim of man-made warming". Basically that leaves amateurs like Gray and McKitrick. In one of his comments Gray asked them to cite one of his Energy and Environment papers. Fortunately it was rejected, or he would have been ruled out as well.

John Mashey examined McLean's background and it seems that while the National Post awarded him a PhD he actually has no scientific qualifications at all, just a Bachelor of Architecture. Which makes McLean's rant against a critic, which was captured by Nexus 6 particularly funny."

My point is the consensus, such as it is, is closer to the denialist view than the popular view of Al Gore etc.

The claim that there is some vast number of scientists that constitute a consensus and that agree with catastrophic warming is not only not science it isn't even correct. We constantly see people pointing out IPCC to supposedly prove this supposed consensus. IPCC isnt all qualified scientists any more than any of these lists are. But more important than that, despite the fact that a pro warming bias is built into the entire IPCC process, the actual body of the IPCC report in fact supports my position rather than that of Al Gore.

When I pointed out that the petition project and other similar things like the Heidelberg appeal all had one thing the IPCC didn't have; the consent and agreement of the people involved. (This is something lacking in the lists of academies etc. in the original post as well.) You ignored it completely as if tiny politically active committees somehow spoke for all.

Personal attacks on a handful of people, each of which is questionable in itself does nothing to refute my stated point. It appears rather to be a deliberate attempt to obfuscate the issue.

If science relied on consensus then the Earth would be the center of the universe and you would fall off the edge. Science is not about consensus, opinion is about consensus. A german physisist,Gerhard Gerlich, demonstrated (in a very long and boring paper) how there can be no greenhouse effect. Do we burn him at the stake? I have seen many explanations about how the greenhouse effect works but no proof. Is it real and can it be proven?

" Definately Not Galileo
A common theme among hardcore denialists, after slowly dragging them around to admit there is a consensus, is an appeal to the Galileo syndrome. "Galileo went against the consensus and he was right!" This is a flawed argument in the climate change debate for many reasons, and it is a Guide entry that is missing for the moment.

I am only bringing it up now, rather than do a proper entry, because of a discussion paper by Ernst-Georg Beck that was presented on Warwick Hughes' blog (no relation to me... to Glenn Beck? I don't know). It is basically a well dressed version of the "there is no anthropogenic CO2 rise" argument. Eli Rabett took the time to take it apart in a rather thorough and scientific manner, especially given the total lack of a credible conclusion Beck arrives at. You can see the featured graph at Deltoid and read Stoat's dismissive opinion of it here.

The irony I want to point out is that Galileo was a forward thinker, reaching into previously untrodden territory. His innovation and imagination helped him see past the prevailing state of human knowledge at the time and go into new ground. What are the denialists doing here? Digging up decades old research with results all over the place, results that lead to all sorts of impossible conclusions and then trying to claim that this is the reality and the new, consistent and refined results are the ones that are wrong. Never mind that this is what progress looks like, this is many minds working to overcome the challenges that caused prior confusion to finally achieve consistent, sensible and reliable data.

But what if you don't like what the new data are telling you? Just chuck it and go back to the old stuff!

Sorry, that is so not Galileo!"
http://illconsidered.blogspot.com/2006/10/definately-not-galileo.html

The term "scientists" is often used in describing signatories. The petition requests signatories list their degree (B.S., M.S., or Ph.D.) and to list their scientific field.[3] The distribution of petitions was relatively uncontrolled: those receiving the petition could check a line that said "send more petition cards for me to distribute".

The Petition Project itself used to state:
“ Of the 19,700 signatures that the project has received in total so far, 17,800 have been independently verified and the other 1,900 have not yet been independently verified. Of those signers holding the degree of PhD, 95% have now been independently verified. One name that was sent in by enviro pranksters, Geri Halliwell, PhD, has been eliminated. Several names, such as Perry Mason and Robert Byrd are still on the list even though enviro press reports have ridiculed their identity with the names of famous personalities. They are actual signers. Perry Mason, for example, is a PhD Chemist.[2] ”

Asked about the pop singer, Robinson said he was duped. The returned petition, one of thousands of mailings he sent out, identified her as having a degree in microbiology and living in Boston. "It's fake," he said.[15]
”

In 2005, Scientific American reported:
“ Scientific American took a sample of 30 of the 1,400 signatories claiming to hold a Ph.D. in a climate-related science. Of the 26 we were able to identify in various databases, 11 said they still agreed with the petition —- one was an active climate researcher, two others had relevant expertise, and eight signed based on an informal evaluation. Six said they would not sign the petition today, three did not remember any such petition, one had died, and five did not answer repeated messages. Crudely extrapolating, the petition supporters include a core of about 200 climate researchers – a respectable number, though rather a small fraction of the climatological community.[16] ”

In a 2005 op-ed in the Hawaii Reporter, Todd Shelly wrote:
“ In less than 10 minutes of casual scanning, I found duplicate names (Did two Joe R. Eaglemans and two David Tompkins sign the petition, or were some individuals counted twice?), single names without even an initial (Biolchini), corporate names (Graybeal & Sayre, Inc. How does a business sign a petition?), and an apparently phony single name (Redwine, Ph.D.). These examples underscore a major weakness of the list: there is no way to check the authenticity of the names. Names are given, but no identifying information (e.g., institutional affiliation) is provided. Why the lack of transparency?[17]"

wikipedia.com

and...........
"Oregon Institute of Science and Medicine

The Marshall Institute co-sponsored with the OISM a deceptive campaign -- known as the Petition Project -- to undermine and discredit the scientific authority of the IPCC and to oppose the Kyoto Protocol. Early in the spring of 1998, thousands of scientists around the country received a mass mailing urging them to sign a petition calling on the government to reject the Kyoto Protocol. The petition was accompanied by other pieces including an article formatted to mimic the journal of the National Academy of Sciences. Subsequent research revealed that the article had not been peer-reviewed, nor published, nor even accepted for publication in that journal and the Academy released a strong statement disclaiming any connection to this effort and reaffirming the reality of climate change. The Petition resurfaced in 2001."
http://www.ucsusa.org/global_warming/science/skeptic-organizations.html

and on the Heidelberg Appeal..............
"Parts of the Heidelberg Appeal do endorse environmental concerns, such as a sentence that states, "We fully subscribe to the objectives of a scientific ecology for a universe whose resources must be taken stock of, monitored and preserved." Its 72 Nobel laureates include 49 who also signed the "World Scientists' Warning to Humanity," which was circulated that same year by the Union of Concerned Scientists (UCS) and attracted the majority of the world's living Nobel laureates in science along with some 1,700 other leading scientists. In contrast with the vagueness of the Heidelberg Appeal, the "World Scientists' Warning" is a very explicit environmental manifesto, stating that "human beings and the natural world are on a collision course" and citing ozone depletion, global climate change, air pollution, groundwater depletion, deforestation, overfishing, and species extinction among the trends that threaten to "so alter the living world that it will be unable to sustain life in the manner that we know." Moreover the Heidelberg Appeal has been, if not specifically misrepresented, at least broadly interpreted out of context, for example, by The National Center for Public Policy which asserts "The appeal warns industrialized nations that no compelling scientific consensus exists to justify mandatory greenhouse gas emissions cuts.""

Yup, clearly ignoring the entire point. You continue to waste my time here. If you can't answer the main points and instead must repeatedly resort to nibbling on the fringes of the petition project it appears you are merely trying to obfuscate the issue.

I am trying to learn things here other than your bias. You seriously are proud that there was 1 fake signature out of 20,000? Even if it was 2000 fakes you would have lost that argument wouldn't you? Please,you've proven my point to any unbiased reader.

if it's such a waste of your time, stay the heck away.
You seriously don't understand that any "fake" signatures, and there were many on both, not to mention the fraudulant article to support the "petition project", you really mean to say that you can't grasp that that in and of itself shows the desperate need to dupe the public with policy driven pseudo-science?
you're point is on your head.

WA, I don't understand why you would even pay attention to the "my list is bigger than yours" type of attitude, which is obviously utter nonsense. Why are you trying to defend that so-called "petition project?" What does that have to do with science and evidence?

Disputing that there is a consensus among climate scientists is downright futile. All sources of information arguing that point are non scientific (Heartland, Cato, Inhofe's office, CO2 science and all that crap). Real scientific organizations (AAAS, AGU, etc) endorse the AGW hypothesis, which is by itself an interesting fact. I find it really funny that "skeptics" both dispute the existence of a consensus and also argue that consensus is meaningless anyway, as Quietman does with a mightily inappropriate comparison.

As for Quietman post about Gerlich's pathetic load of dung, Rabett Run has more on that than anyone really needs to know. And to answer his question, there is no doubt about the radiative properties of CO2 and the reality of the GH effect. It can be precisely measured in the lab, and if there was no GH effect, this planet would be an ice covered rock. The Gerlich paper is also funny in the sense that it denies the very existence of a GH effect at all but, later, the authors questioned about Venus go on explaining Venus' temps by GH effect from other sources than CO2. It's perfectly grotesque, a fine example of the worst BS that denialism can produce.

The quality of skepticism here is on the way down if that's the kind of stuff we're going to talk about. Well, BTN had already set the bar so far down that we might have a margin anyway, but still.

This my thought of the day to you, Quietman, and others. You can not apply extreme scrutiny to the CO2 hypothesis and lower scrutiny to alternate explanations. I know that it makes for a lot more work but that's the only way. If you apply the same extreme scrutiny to these other alternate explanations, what is left of them? Have you even tried (sincerely)? If not, you can not call yourself a skeptic in the true sense of the word. In my experience, if you try to take apart these alternate theories with any eagerness comparable to what "skeptics" use against the CO2 hypothesis, there is nothing left, zilch, nada. That's one reason why I'm skeptical about climate skepticism.

WA: "The claim that there is some vast number of scientists that constitute a consensus and that agree with catastrophic warming is not only not science it isn't even correct."

Here is a strawman so big, it's more akin to the Chinese straw dogs. Let's merrily burn it.

Indeed, it's not correct at all. The SCIENTIFIC consensus is that there is warming, happening quite fast, and that the massive CO2 release from the burning of fossil fuels is a major contributor to it. That is the real consensus.

I do indeed think it is clear that the public is being duped. I think it is deliberate and I think the AGW alarmists are the ones doing it.

The "many fake signatures" is both clearly incorrect and irrelevent. By your own references over 90% were verified.

Phillippe I don't agree with your way of stating the consensus though It isn't far enough off to argue.

On your double standard point though, Phillippe, that is exactly the contention I have been making from the other side of the issue for a long time so it is kind of funny.

The correct hypothesis has to defeat all the others. It has to pass the experimental test and make predictions that other hypothesis don't. Being experimentally supported is the beginning of this; that isn't enough to prove it, but at this point we haven't even got that. Being only not much worse than the other explanations is not enough. Holding the accepted theory to the highest standard is what a scientist is supposed to do. It only takes one thing to prove it wrong.

The perhaps painful truth is CO2 has not been a major cause of climate change in the past, despite levels many times the current level. In order to believe it is about to cause huge consequences today when it never did in the past you need some pretty convincing proof or some new physical reality.

John I am pretty impressed with how current you keep your articles references.

"The perhaps painful truth is CO2 has not been a major cause of climate change in the past"

That may be because there has not been a release of CO2 on the scale we experienced these last 150 years during the 600k years of very stable climate the planet has been through. If you try to go farther in time, there is too much uncertainty to do informative comparisons. There is nothing to prove that a massive injection of CO2 in an otherwise stable climate can not have serious consequences. And, by the way, spare me the exaggerations that have nothing to do with what the research actually shows and suggest is possible. I do not pay more attention to exaggerated claims from advocay groups, whether they're from one side of the spectrum or the other.

And I also maintain that, if you are a true skeptic with physics background, you should be screaming bloody murder to the flat-earthers like Gerlich. If not, then you're applying a double standard far worse than anything you claim is practiced in the scientific peer-reviewed litterature.

Re 23 Wondering Aloud
'Not all that glisters is gold'
And The Oregon Petition of Science and Medicine 'Petition Project' Review, now updated with a change in authors was neither peer-reviewed (despite explicit claims)), nor science - it was deceptive pseudo-science, deliberately formatted to appear as if it were a NAS publication (and therefore peer-reviewed).

For an excellent insight into the Oregon Petition Document, see:
http://tinyurl.com/nt38z

This is from a Professor who frankly admits that he was nearly fooled by it.

Enough people were fooled that the National Academy was inundated with calls asking if it was their new position and had to issue a news release.
Quote
''The Council of the National Academy of Sciences (NAS) is concerned about the confusion cause by a petition being circulated via a letter from a former president of this Academy. This petition criticizes the science underlying the Kyoto treaty on carbon dioxide emissions (the Kyoto Protocol to the Framework Convention on Climate Change), and it asks scientists to recommend rejection of this treaty by the U.S. Senate. The petition was mailed with an op-ed article from The Wall Street Journal and a manuscript in a format that is nearly identical to that of scientific articles published in the Proceedings of the National Academy of Sciences. The NAS Council would like to make it clear that this petition has nothing to do with the National Academy of Sciences and that the manuscript was not published in the Proceedings of the National Academy of Sciences or in any other peer-reviewed journal.
The petition does not reflect the conclusions of expert reports of the Academy.''
End quote

http://tinyurl.com/38nqdj

Note: Seitz, Baliunas & Soon are all associated with the ExxonMobil funded George C Marshall Institute!
Seitz was a solid-state Physicist.
Baliunas & Soon are Astrophysicists.
Arthur Robinson and his son Zachary are Chemists.

Note that none of the authors of this purportedly climatological paper are climatologists!

The updated version of this OISM 'review' was published in that well known organ of climate research - The Journal of American Physicians and Surgeons (2007).
Little wonder that it survived peer review.

Apparently the previous 1998 version was later published in Climate Research - A Journal that has had serious problems with its criticised peer-review process, notably under the editorship of Chris de Freitas, under whom numerous editors resigned in protest. I don't know when the 1998 version was published, or whether the Editor was de Freitas. But there seem to have been some pretty suspect papers published in CR.

"That may be because there has not been a release of CO2 on the scale we experienced these last 150 years during the 600k years of very stable climate the planet has been through."

Hold on, did anyone else notice that? 600k years of very stable climate? The last 600k years has been a torrent of climatic change. So if by "stable" you mean "always changing between extremes," then yes, you are correct. Beyond that, the Earth's climate has never really been stable.

Robert, these extremes are very well constrained compared to numerous changes that happened before that period. It is fair to say that the climate of the past 600k years has been quite stable compared to the climate of times before that, because those "extremes" remain within a certain range. Even the periodicity of the changes remains overall nicely consistent. So my comment is far from being ridiculous.

This page gives a quick glance at very long term variability:
http://www.scotese.com/climate.htm

I have ran many times into the argument that climate has changed to extremes in the past and they always call on paleoclimate examples from way before the ice core records, especially hot house periods of the mesozoic times, which are of little relevance to our situation.

Besides, it is interesting to note that the 2 largest mass extinctions of the geological record happened in hot times (P/T and Cretaceous).

It is also interesting to look at how CO2 has changed during these 600k years compared to what has happened in the (very) recent past. There is no precedent in the ice core record to such an injection of CO2. Nothing even remotely comparable to it. See this link, slide number 8.
http://ec.europa.eu/research/environment/pdf/descriptions/raynaud_ipy_bxl07.pdf

You say:
"Robert, these extremes are very well constrained compared to numerous changes that happened before that period. It is fair to say that the climate of the past 600k years has been quite stable compared to the climate of times before that, because those "extremes" remain within a certain range. Even the periodicity of the changes remains overall nicely consistent. So my comment is far from being ridiculous."

and then you say:
"I have ran many times into the argument that climate has changed to extremes in the past and they always call on paleoclimate examples from way before the ice core records, especially hot house periods of the mesozoic times, which are of little relevance to our situation."

This seems slightly peculiar--you use that very comparison in your first paragraph. Regardless, the last 600,000 only appears stable when compared to the vastly different time scale of the previous 600myr (such a comparison is not useful). Essentially your argument boils down to the "the last 600k years have been stable in that they are consistent in their extremes and periodicity." The belief in constant change as "very stable climate" seems misplaced.

Then you say:
"Besides, it is interesting to note that the 2 largest mass extinctions of the geological record happened in hot times (P/T and Cretaceous)."

They did occur in "hot times," but the mechanism behind these extinctions is considered to be volcanism and/or meteor impact-- blocking sunlight and preventing photosynthesis. On the other hand, the Ordovician-Silurian extinction (3rd largest) occurred during the transition to one of the largest Ice Ages in the past 600myr. Anyhow, this seems irrelevant to my response (39) above. Your last paragraph also seems irrelevant--I don't disagree that CO2 is higher now than any time in the last 600kyr.

Change alone does not make unstability. Perhaps a comparison with weather would be useful. The weather changes continuously along the year, yet we deal with it just fine so long as nothing happens like 4 months without rain or freezing in june.

The examples of hot house as in the mesozoic times are commonly used by advocates who argue that because it has been very hot before, it's OK to go that route again now. The fact that the world and the biosphere were vastly different in these times is what makes that argument irrelevant, not the climatological elements themselves. Those advocates often argue that warmer is better, yet mass exctinctions have happened during these periods, indicating that a hot house does not guarantee against them.

The cause of the Permian extinction is unknown. I don't know any that has been established for the Ordovician. So the volcanic/collision explanation for mass extinction applies with any level of certainty to the Cretaceous only.

Philippe said:
"Change alone does not make unstability. Perhaps a comparison with weather would be useful. The weather changes continuously along the year, yet we deal with it just fine so long as nothing happens like 4 months without rain or freezing in june."

You have invoked two comparisons which are irrelevant: Weather and climate more than 600kya. And your last sentence seems odd--based upon other interglacials, we have been in late november for the last 2000 years and the first frost still hasn't come.

Then Philippe said:
"The examples of hot house as in the mesozoic times are commonly used by advocates who argue that because it has been very hot before, it's OK to go that route again now. The fact that the world and the biosphere were vastly different in these times is what makes that argument irrelevant, not the climatological elements themselves. Those advocates often argue that warmer is better, yet mass exctinctions have happened during these periods, indicating that a hot house does not guarantee against them."

I don't know who these "advocates" are but this does not seem to be in either of my responses.

"The cause of the Permian extinction is unknown. I don't know any that has been established for the Ordovician. So the volcanic/collision explanation for mass extinction applies with any level of certainty to the Cretaceous only."

The cause for an ancient extinction is never "known." It has been speculated that the Permian extinction was caused by a similar event to the one that caused the Cretaceous--volcanism and/or meteor impact.
The Ordovician-Silurian extinction occurred at the transition to one of the largest Ice Ages in the last 600myr. So while he cause is not "known," the current running theory speculates that the cause is the somewhat rapid decrease in temperatures.

When you compare the last 600kyr to the previous 600myr, of course the climate looks "very stable," but that is not a meaningful comparison--it's useless. Not only is the time scale vastly different, but the mechanism for change is as well (also, time periods before the ice core record are far less certain). No great departure from extremes does not necessarily equate to "very stable climate."

The weather comparison is not useless or irrelevant. Events like freezing in june or 4 months without rain are elements of instability, if they turn into a trend. Just like being in late november and still waiting for a frost to come, if it happens more and more regularly (as it has). About climate, a warming like the one seen lately, while temps should be stable in our kind of time scale, is an element of instability. A massive injection in the atmosphere of a gas ike CO2 (whose physical properties are known) is also an element of instability.

My comparison using November and late frost was meant to imply that this interglacial has gone on several thousand years too long, with respect to previous interglacials.

You say:
"About climate, a warming like the one seen lately, while temps should be stable in our kind of time scale, is an element of instability."

If the recent warming is an element of instability, then you have just contradicted your previous assertion that we have had 600kyr of very stable climate, because events similar to the recent warming have occurred a multitude of times in the last half a million years. The recent warming is hardly unprecedented.

"The recent warming is hardly unprecedented." Even in periods of end interglacial times, when temps would be expected to slowly cooling down, as you mentioned? Even on that kind of time scale, a blink of an eye really?

Philippe wrote:
"Even in periods of end interglacial times, when temps would be expected to slowly cooling down, as you mentioned?"

Is it a "period of end interglacial time"? Well it depends on what you think causes the glacial periods--if the mechanism isn't there, then it isn't going to happen. If you believe the Milankovitch cycles are what initiates the glacial/interglacial, then we are still a ways from another glacial period. So it is not inconceivable that the planet would experience a warming at this time.

Then he wrote:
"Even on that kind of time scale, a blink of an eye really?

OK, but can you substantiate with references?"

If you want to take issue with the idea that the planet has had warming similar to the recent warming on both the time scale and in magnitude, be my guest. It would be a losing battle. As for references, all one has to do is a little searching--this interglacial, the last glacial, the last interglacial, etc. It won't be too hard to find warming of this magnitude in this time scale.

All of you do realize of course that there is a very basic premise involved: If there was a consensus, there would be very little dissent. Given the extremely large amount of dissent, we must assume one of two things:
1) there is no consensus or
2) the consensus is not what the IPCC claims it to be.

The so-called "large amount of dissent" is just a small group of people making a lot of noise again and again.

Remember the claim that there were 19,000 scientists disputing global warming? During the New York denialist conference ("2008 International Conference on Climate Change"), it turned out there were only _19_ scientists. Looks like the number 19,000 is off by a factor of 1,000.

As an added bogus, the logo for the denialist conference was a loudspeaker.